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An odd question about dithering

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10 replies to this topic

#1 stars n planets

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Posted 05 December 2020 - 04:47 AM

If your PA is slightly off and you are guiding, could you avoid dithering? I cant get my head around if you get image shift from sub to sub.

Thanks

#2 Roger123456

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Posted 05 December 2020 - 04:51 AM

This is what causes walking noise. It needs randomness to be effective in averaging.
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#3 stars n planets

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Posted 05 December 2020 - 05:14 AM

This is what causes walking noise. It needs randomness to be effective in averaging.


So would a bad Polar alignment cause field rotation as the guide star is a single point of reference??

#4 sharkmelley

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Posted 05 December 2020 - 05:14 AM

If your PA is off and you are guiding then you will end up with field rotation.  The worse the PA error, the worse the field rotation.  This will potentially cause walking noise in circular arcs.

 

Mark



#5 stars n planets

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Posted 05 December 2020 - 05:17 AM

If your PA is off and you are guiding then you will end up with field rotation. The worse the PA error, the worse the field rotation. This will potentially cause walking noise in circular arcs.

Mark


But wouldn't the fact that the points of signal (the stars) will have shifted, be the same as what dithering does? Sorry trying to get of an understanding of this

#6 sharkmelley

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Posted 05 December 2020 - 05:21 AM

But wouldn't the fact that the points of signal (the stars) will have shifted, be the same as what dithering does? Sorry trying to get of an understanding of this

Yes all the stars except the guide star will shift.  It's true that dithering also shifts the stars.  The difference is that dithering produces random shifts whereas any kind of drift or rotation will create obvious trails.

 

Mark


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#7 stars n planets

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Posted 05 December 2020 - 05:25 AM

Yes all the stars except the guide star will shift. It's true that dithering also shifts the stars. The difference is that dithering produces random shifts whereas any kind of drift or rotation will create obvious trails.

Mark


Ahhh yes. I see its not random and is a pattern it self. Im setting up a dual imaging system on 2x asiair pros on a single mount. They dont sync so im looking at a solution for dithering. I may have to see if images come out good or bad :(

#8 imtl

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Posted 05 December 2020 - 05:46 AM

If I may ask, did you get a SINGLE imaging system working flawlessly (whatever that means...confused1.gif )? Its just from your question it seems that you might be just beginning this hobby. I might be wrong of course.



#9 stars n planets

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Posted 05 December 2020 - 05:49 AM

If I may ask, did you get a SINGLE imaging system working flawlessly (whatever that means...confused1.gif )? Its just from your question it seems that you might be just beginning this hobby. I might be wrong of course.


Hi

Been imaging for about a 2 years. Dithering is something i do already. My images are ok with the single imaging system i already have.:)

#10 imtl

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Posted 05 December 2020 - 06:00 AM

Well, don't mean to tell you how to run your show of course but maybe better to perfect single imaging system first. Just saying.

In any case, you could consider dropping the dual asiair pro and just have a mini pc controlling everything. Its going to give you much better control of things, and I think you'll find its actually cheaper than 2 asiair pro.


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#11 stars n planets

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Posted 05 December 2020 - 06:09 AM

Well, don't mean to tell you how to run your show of course but maybe better to perfect single imaging system first. Just saying.
In any case, you could consider dropping the dual asiair pro and just have a mini pc controlling everything. Its going to give you much better control of things, and I think you'll find its actually cheaper than 2 asiair pro.


True. But as i already have the kit, all i would loose is time i guess. If it doesnt work the p.c. route it may have to be.

Thanks :)


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